29

29 is the smallest multidigit prime number whose product of digits of its cube is also a cube: 29³ = 24389 and 2 x 4 x 3 x 8 x 9 = 1728 = 12³. 29 is also a Sophie Germain prime because 2 x 29 + 1 = 59 is prime.

29 has a representation as a sum of two squares: 29 = 2² + 5².

29 is the smallest prime equal to the sum of three consecutive squares: 2² + 3² + 4² = 29.

The 29th power of 2 is the largest power to 2 to have all different digits.

29 is the seventh Lucas number.

29 and 31 form a twin prime pair.

29 is the hypotenuse of a primitive Pythagorean triple: 29² = 20² + 21².



The extra day in a leap year is February 29.

Source: Number Gossip